1. Field of the Invention
The invention generally relates to position detection apparatus for use in measuring and gaging systems. More particularly the invention concerns probe contact detection apparatus for providing an indication of probe contact with a workpiece.
2. Description of the Prior Art
Many known position detection or touch probes conventionally use mechanical contacts as the contact sensor. Such contacts are expensive to manufacture and have limited resolution. Additionally mechanically moving switch contacts are subject to wear and corrosion.
Another type of known touch probe avoids the corrosion and wear problems of mechanical switch contacts by arranging the probe to severely attenuate a radio frequency signal upon contact of the probe with a metallic workpiece. One such prior art device is taught in U.S. Pat. No. 4,118,871--Kirkham. Such arrangements are prone to electromagnetic noise interference with the radiated radio frequency signal, and this interference can lead to false indications of probe contact with a workpiece.
Also related to this invention, although less directly, is that prior art concerned with wireless transmission of dimensional gaging data such as disclosed in U.S. Pat. No. 3,670,243--Fougere et al., U.S. Pat. No. 4,130,941--Amsbury, and pending U.S. patent application Ser. No. 6-182226, filed Aug. 28, 1980, now U.S. Pat. No. 4,328,623 and assigned to the same assignee as the instant invention.
A need has arisen for touch detection apparatus with high resolution and immunity to electromagnetic noise, capable of wireless transmission of an indication of the occurrence of probe contact with a workpiece. A need also has been demonstrated for touch detection apparatus with the added capability of accepting a variety of position determining transducers.